THALAMIFLORjE. g7 



119. The Buttermps (Fig. 9, i, 3) stand at the head of 

 this Subdivision, and of course at the head of the flower- 

 kingdom ; they include the Columbine (Fig. 154) and Cle- 

 matis (Book-cover, side). 



In this Order (with the exception of the ovaries in Nigella) all the 

 floral parts are distinct and free (Pig. 9, 3). Many of the plants are 

 marshy or aquatic in habit; and these ("Water Crowfoot, etc.) singu- 

 larly resemble the Water-Plantains in Endogens ; except that they are 

 exogenous, and their floral number is Pive. The May-apple (in the 

 Barberry family) and the Magnolia have their floral parts in threes ; and 

 they r.esemble the Lilies in the appearance of their petals. These 

 Orders, therefore, seem to be a sort of link between the two Sub-classes 

 Endogens and Exogens. But we must remember that "classification 

 is a net-work, not a chain," as the botanist Robert Brown has said. 



120. Exogenous Growth. — The 



embryo here has two cotyledons, 

 which are opposite. The leaves 

 are either opposite, alternate, or 

 whorled ; they are net-veined (Fig. 

 74). The stem is differentiated 

 into pith, wood, and bark (Fig. 

 81) ; its increase is by concentric 

 layers of wood-bundles around a 

 central pith. The pith is purely _ 



cellular. The newest WOOCZ is al- rio.81.—TiansverBe section of an 

 ,.1,1 1 i 1 p exogenons tree 9 years old; with 



ways outside the last layer or central pith, 9 wooa-circies, 1 for 

 wood-bundles, and for this reason ZXlli.' "'"' ''^■'''-'="'=''= °"'"'*° 

 the growth is called exogenous 



(outside growth). The bark is distinctly differentiated from 

 the wood ; its newest growth is outside the wood but inside 

 the other layers of bark. (The stem and its action are 

 treated in the Lessons in Part Second, Phytotomy.) Ob- 

 serve these characteristics : 



I. Covered Seeds. — Embryo with radicle, plumule, and 

 2 opposite cotyledons, with the plumule between them. 



II. Flowers with perfect pistils and stamens; perianth 

 sometimes wanting, but usually conspicuous and differen- 

 tiated into calyx and corolla. 



Ill Floral parts quinary — Five, or some multiple of five 

 (Fig. 82, 6) ; rarely two, or some multiple of two (Fig. 82, 



